The field of the invention relates to foam insulated refrigerators, and more particularly relates to apparatus for draining water from a defrosting evaporator through the insulation space between the liner and the outer casing, and the method of fabricating such apparatus.
As is well known, most domestic refrigerators are insulated using a so-called foam-in-place process. That is, a plastic liner is positioned within the outer metal shell or casing with a space between the liner and the shell. Foam insulation is then injected under pressure into the space between the liner and the shell, and the foam flows along the bottom, sides, and top so as to fill all voids in the space. Subsequently, the foam solidifies and becomes rigid insulation.
When a defrost refrigerator is foamed-in-place, a small passageway is provided through the insulation space so that when ice is melted from the evaporator, the water can drain from the evaporator through the insulation to a drain pan underneath the refrigerator. There are a number of design criteria placed on a conduit which channels the defrost water through the insulation space. First, because it is preferable to install it before foaming, it must withstand the temperature and pressure of the foam injection process without collapsing or leaking foam. Also, because of manufacturing tolerances, it must allow for misalignment between an aperture in the liner and a corresponding hole in the shell. Further, it must seal to the liner during the foam injecting process and thereafter provide a watertight seal so that water within the liner cannot leak into the cabinet insulation. Also, it must seal to the shell during the foam injecting process and thereafter provide an airtight seal to prevent water vapor from entering the insulation from the outside.
Generally, prior art conduits or drain funnels have been made from either flexible rubber or rigid injection molded plastic. A rubber conduit seals to the liner and shell like a grommet, and its inherent flexibility allows for cabinet misalignment. However, because it is flexible, the pressure of the foam tends to collapse a rubber conduit unless a temporary plug is inserted through the conduit before the foam is injected. Inserting and removing a plug means extra steps in the fabrication process, and occasionally a plug may be forgotten and left in the conduit thereby requiring a subsequent service call when the defrost drain clogs during operation. Also, because rubber conduits have been relatively large so that the temporary plugs can easily be inserted and removed, screens have been used to cover the large drain openings so that debris will not drop into the rubber conduits thereby clogging them; the screens increase labor and parts costs. Another drawback of rubber conduits is that they are more expensive than rigid injection-molded plastic parts.
Rigid injection-molded plastic funnels or conduits stand up to foam pressure without internal reinforcement such as provided by a temporary plug. However, problems occur in sealing and also in allowing for misalignment between the liner and the shell. One prior art approach is to hand caulk the funnel and then seal it to the liner. This approach requires constant attention of the assembly operator to ensure that there is a good seal around the entire perimeter of the funnel. In a small but very expensive percentage of these caulk seals, foam leaks into the drain funnel. These leaks require an expensive procedure of turning the cabinet over, digging out the funnel, cleaning it, and then resealing it. Also, since the new funnel is not foamed-in-place, it may not have a good seal to the liner. Furthermore, spring fixtures have been used to hold rigid plastic funnels in place until after foaming. Sometimes, these spring fixtures become unhooked and fall out of place during foaming thereby resulting in foam leaks. Also, the use of a spring fixture requires extra parts and steps during the manufacturing process, and after removed, the spring fixtures have to be carried back to an earlier station on the assembly line.
Another prior art rigid plastic approach uses screws to clamp a gasket between the funnel flange and the liner. This makes leaks unlikely and holds the funnel in place without the use of a spring fixture, but it makes misalignment of the liner and the shell a greater problem. One approach to this misalignment has been to have an oversized hole in the shell, and then use a plug button to cover the gap between the funnel and the perimeter of the hole. Specifically, the plug button has a hole in the center sized to fit the drain funnel end. To allow for misalignment, the hole is slit so that the drain funnel can exit the hole off center. After installing the funnel and plug button, hand-applied sealer is used to close the slit. This technique also requires close operator attention, and a certain percentage of such seals have developed leaks which are expensive to repair.